CN1663197A - Method and communication station for transmitting data - Google Patents

Abstract

The invention relates to a method for the error-monitored transmission of data (D) via interfaces (V11, V13, V21, V23) of a multi-step communication system, in which said data is transmitted from a transmitter station (SS) to a data-receiving station (RS) via at least two relay stations which are connected therebetween and receive and further transmit the data parallel to each other, whereupon the data is retransmitted if the transmission has been insufficient due to a request from the receiver end and/or due to the lack of a confirmation (ACK) from the receiver end. In order to increase performance while reducing power consumption of the system, the request or confirmation is generated only by the receiver station and is sent back to the transmitter station. The relay stations consequently do not generate any confirmations or requests.

Description

Method and communication station for transmitting data

The invention relates to a method for error-monitored data transmission via a parallel interface of a multi-hop communication system having the features of the preamble of claim 1, or to a communication station implementing such a method.

In a multi-hop communication system (also known as a Multi-Hop communication system), data is transmitted from a transmitting station to the nearest receiving station either directly through an intermediate station or a relay station or through multiple transiting intermediate stations or relay stations. In addition to data transmission via a single forwarding relay station, data can also be transmitted via multiple consecutive relay stations, which is also referred to as multi-hop. Furthermore, especially in shared wave network (SFN: Single Frequency Network) communication systems, one and the same type of signal and thus one and the same type of data can be received simultaneously or with little time shift by multiple relay stations and shared ie simultaneously or relatively short time-shifted and transmitted on the same frequency either directly to the receiving station or to another relay station. Here, a pre-emphasis method or a de-emphasis method may be used in the relay station to improve efficiency. In order to guarantee error-free data transmission, communication systems of this type or other use per se known error detection and error correction methods, such as automatic request to repeat the transmission of original or updated data packets (ARQ : Automatically request resend). It is also known to use a so-called cyclic redundancy check (CRC: Cyclic Redundancy Check). Here, the methods are reapplied for each single transmission, i.e. for each transmission from a transmitting station to an adjacent relay station, for each transmission from one relay station to another and for each transmission from a Each transmission from the relay station to the receiving station. Although these measures ensure that the data arrive at the receiving station as error-free as possible via as many paths as possible, they have the disadvantage of the high computational and time costs associated with this. In addition, high energy consumption is also associated with this method measure, since on the one hand the unpacking, decoding and verification of the received data in the relay station, as well as the request for re-delivery or re-encoding and forwarding consume energy and finally repeat the transmission Retransmitted data packets also consume energy.

The object of the present invention is to develop a method for error-monitored data transmission via a parallel interface of a multi-hop communication system, in particular with regard to the processing costs of the entire system, and to propose a communication station implementing such a method.

This object is achieved with the features of claim 1 , a method for error-monitored data transmission via a parallel interface of a multihop communication system, or with a communication station with the features of claim 9 .

Preferred embodiments are the subject matter of the dependent claims.

Since the acknowledgment or request for a new data transmission is only generated by the receiving station, the so-called last station in the transmission chain, this station must also only monitor the received data with a satisfactory reception quality. When a satisfactory reception quality is recognized, this station also only transmits an acknowledgment or request thus generated in the direction of the station that originally transmitted the data. In the simplest case, the intermediary relay stations are only used to forward received data or to forward received acknowledgments or requests. In such a simple case, it is correspondingly possible to omit the check of the forwarding of the received data in the relay station, which enables a fast forwarding and lower energy consumption.

A relay station which, in order to relay received data, checks that the quality of reception is insufficient and does not relay or relay data related thereto, or maintains or disconnects the data communication connection depending on the quality of reception, although the relay station requires energy and requires The time to receive the data is checked, but energy is also saved in the end by interrupting the handover and requesting a new data transmission. Since in this type of communication system the originally transmitted data is transmitted over many parallel data paths, there is a sufficiently high probability that in the event of a loss of data on a transmission path and subsequent In the case of deactivation, the original data arrives at the intended destination station or receiving station despite passing through at least one or more other parallel transmission paths. A communication system or a method measure is therefore preferred in which the data are only transmitted via a relay station which satisfies the requirements well or receives the data in an error-free manner which is sufficiently satisfactory.

When the preferred relay station independently determines whether the data received is of a sufficiently good quality for the relay, a method is particularly preferred in this case, in which the information of the relay stations on the parallel transmission path is also taken into account for the determination. If a relay station on a parallel path informs that it can relay received data for transmission with good or high quality relay, then the parallel relay station notified of this need not make additional transmissions, possibly even poorly. received data. This is when parallel data paths cross each other or each relay station can receive relayed data from other relay stations in its surroundings.

Many error correction methods or error detection methods known per se in relay stations can preferably be used, wherein these methods are only used to detect the quality of the received data to be forwarded, but not to detect retransmissions in the case of poor reception quality ask.

A method of this type is particularly preferably used in communication systems in which the various transmitting and receiving stations and relay stations all communicate on a single frequency. These conditions exist in particular in decentralized, ie self-built, communication networks, as are typical for specialized communication systems.

In the terminating receiving station, the data received via the different parallel paths parallel to one another and superimposed are preferably superimposed and co-processed, so that a further quality improvement can be achieved by means of statistical average formation or the like.

Especially in relay stations for condition-dependent forwarded data, a high overall data rate, i.e. a high retransmission quality, can be obtained at the receiving end, in that the data received by the receiving end can There is an overall qualitative improvement.

A communication station implementing such a method may be a transmitting station, a receiving station or a relay station, but may also have two or all three functions in a combined manner. A communication station of this type has, in addition to receiving, according to its purpose, a transmitting device and an analyzing device, which may be part of the station's own control device and which is designed to analyze the received data according to its reception quality.

An exemplary embodiment and developments described here will be described in more detail below with reference to the drawings. In the picture:

Figure 1 shows a communication system with a plurality of stations communicating via parallel data communication connections in the form of a block diagram, and

FIG. 2 shows, in the form of a block diagram, different approaches for processing relayed received data in a relay station.

As can be seen from FIG. 1, an exemplary communication system MHSFN has a number of stations communicating with each other. For example, a multi-hop or multi-hop (MH) communication system is shown as a communication system which is formed as a shared wave radio network (SFN: Single Frequency Network). However, transmissions on other communication systems, in particular transmissions on dedicated communication systems are possible.

A situation is shown in which a transmitting station SS transmits data D to a receiving station RS. In this case, it is assumed that the distance between a transmitting station SS and a receiving station RS is so great that a direct transmission between the two stations via a direct communication link is not possible. The transmitting station SS transmits its data D to different switching stations through multiple communication interfaces V11, V12, V13. These different switching stations are referred to below as relay stations HS1, HS2, HS3 for the sake of simple distinction. For example, the relay stations HS1, HS2, and HS3 can identify on the data header (header) of the received data packet, which refers to the received data D to be transferred, and transfer the received data D according to the destination station. The direction is also switched according to the direction of the receiving station through other communication interfaces V21 and V23. Preferably, the communication interfaces V11 , V12 , V13 , V21 , V23 are wireless interfaces, which all operate with the same or unique frequency. For the case where the receiving station RS is already within the transmission range of the relay stations HS1, HS3, the received data D to be forwarded can be directly transmitted to the receiving station RS. In other cases the transmission can take place via further intervening relay stations.

After the data D has been received, it is checked by the receiving station RS whether it is sufficient to receive these data without errors. For the check, conventional error detection and error correction methods known per se, such as ARQ and/or CRC, are used. According to such an analysis, the receiving station RS transmits an acknowledgment ACK regarding the sufficient reception quality and/or a request in the direction of the original transmitting station SS for retransmission or retransmission of the originally transmitted data D. The acknowledgment ACK or the request can again be transmitted via the direct communication link or a plurality of parallel communication links V21 , V11 , V23 , V13 , V22 , V12 with switching by the relay station HS1 , HS2 , HS3 . The transmitting station SS then, depending on the confirmation ACK and the request, delivers new data D or new data packets, or causes repeated delivery and optionally updated delivery of the original data.

According to the preferred embodiment, the data D received in the relay stations HS1, HS2, HS3 in the preferred manner for the transfer cannot simply be transferred without checking, but should be based on the quality or data received before the transfer. Quality is checked. If the relay station HS2 determines that the data quality of the forwarded and received data D does not meet the requirements, or the data D is received with errors, the relay station HS2 does not establish the communication connection V22 for forwarded and received data D. As a result, the corresponding data path V12 , V22 is interrupted, which data path V12 , V22 was established originally from the transmitting station SS via the second relay station HS2 to the receiving station RS. In particular, the second relay station HS2 also prevents the original or updated original data D from being retransmitted.

In the relayed relay stations HS1-HS3, in addition to the receiving device R and the transmitting device S, as well as the control devices and memory normally required for operation, devices and functions for checking the relayed received data are correspondingly provided. In particular, an evaluation device A is provided for this purpose, which is a component of the central control device of the relay stations HS1-HS3.

Further devices and/or functions are preferably used to carry out a pre-emphasis or de-emphasis method, by means of which, for example, a superimposition of a planned signal can reach the receiving station RS and optionally further relay stations. For example, methods known per se such as phase or equal gain, maximum ratio or selective distortion are used. Also combining or augmenting and other pre-emphasis techniques are possible.

According to another embodiment, communication with each other using different relay stations HS2, HS3 is also possible. Communication is also possible via a corresponding interface VH, which can preferably be designed as a wireless interface, but in principle can also be designed as a wired interface. Information about the forwarding of the received data D or about its reception quality can thus be transmitted. This makes it possible for the third relay station HS3 to communicate this fact to the second relay station HS after receiving the data D with a very good reception quality, and this second relay station HS receives this same data D in parallel as a parallel station, but This is however received with very poor reception quality. In such a case, the relay station HS can prevent the forwarding of the forwarded data D with poor reception quality, because the same data D can be transmitted with a better forwarding quality via the parallel data path SS-HS3-RS .

In general, data processing can be performed on the data received by the transfer before the transfer in the relay stations HS1-HS3. In this case, the type of further processing and forwarding or forwarding can be set under different parameters. For example, the signal-to-noise ratio (SNR) can be analyzed and calculated at the input of the transit relay stations HS1-HS3. It is also possible to determine the number of correction bits in the Viterbi decoder, or take into account the result of the cyclic redundancy check (CRC). A method of equalizing and amplifying the received signal without further demodulation is particularly preferred as a processing technique. In the relay stations HS1-HS3, which check the forwarded received data, the received data D are demodulated and decoded in a suitable manner in order to be able to carry out the actual analysis. Not only is the analyzed data D or data packet re-encoded and modulated, and the implementation of the subsequent switching is possible, but also the data D received by the original switching is saved in the scratchpad, so that if the doubled data set is demodulated, After decoding and analysis is enough to be regarded as a transfer, then the transfer is performed in an unchanged manner from the temporary register, and such an implementation is also possible. The method of retransmitting faulty or insufficiently received data packets can preferably be deactivated if the station receiving the data D is not a destination station but only a relay station.

In the context of forwarding or switching, pre-emphasis is also possible in addition to recoding and modulating the data D or data packets. In particular, after de-emphasis, amplification and even pre-emphasis, switching of the received signal or received data D can be performed.

In principle, applications are possible not only in centralized but also in decentralized or self-organizing networks. The exchanging of the parameters mentioned at the outset between individual stations, in particular between relay stations on parallel data paths, can be used particularly preferably, as described at the beginning of the article. However, it is also possible to use only the parameters used in the own station for the analysis, for example by means of error detection and error correction methods known per se. In this case, the use of error correction methods in the case of relay stations can be limited to the part of error detection, wherein the error correction part is only used if no retransmission is required for this, but the transmission of the data takes place via a sufficient number of parallel The data communication connection can be guaranteed. The same applies to the error detection method, which is preferably limited to the detection of errors in the presence of relay stations, wherein a corresponding notification of the error detection is to be prevented.

In the case of communication between adjacent stations, in particular relay stations HS2, HS3, on the one hand only the analysis results can be transmitted directly to the adjacent stations, but it is also possible to use negotiation between such adjacent stations Alternatively, analysis results or calculation results are negotiated, so that adjacent stations can determine, in order to conclude this type of negotiation, via which negotiated station HS3 the data is to be forwarded.

FIG. 2 serves to diagrammatically illustrate different modifications of the illustrated embodiment. Here, the focus is on the structure of the analytical calculation method. In simple terms, it can be assumed that, for example, only a single parameter is used, which is the result of a cyclic redundancy check. Furthermore, in a simple example it is assumed that the relaying of the received signal at the intermediate station or relay station HS1-HS3 can be fully demodulated and decoded. In this case, an error correction method is based on a 2-hop SFN communication system, in which an end-to-end communication link of error-correcting ARQ is implemented. Error correction, which is known per se for the individual communication links, can be selected according to the scheme described now. As a result, the originating station SS does not receive an acknowledgment for the data or data packets, which were correctly received by the relayed relay stations HS1-HS3. Correspondingly, the safety device of the first jump is not separated. Only the receiving station RS acknowledges that the packets were received correctly, so that in the absence of an acknowledgment, the transmitting station SS repeatedly transmits a packet with a missing receipt acknowledgment.

There are various options for processing the data D or data packets for the relay station HS. According to a particularly simple embodiment a), unconditional switching can take place in the relay station HS. In this case, it can happen that the data packets received by the relay are faulty or that the signal-to-noise ratio of the relay is poor. In this case calculation parameters etc. are eliminated.

The data D received by b) is therefore preferably forwarded in conjunction with or in connection with the condition. These conditions can be evaluated independently of one another in individual different parallel relay stations HS or with the aid of information from all or a plurality of relay stations HS2 , HS3 in communication with each other. Correspondingly, there are two improved schemes. In the simpler case c), only an in-station evaluation of the forwarded reception data D is carried out. If the analysis data have a sufficiently good data quality, a switch in the direction of the receiving station RS can be initiated. If the data quality does not meet the requirements, a transfer in the direction of the receiving station RS is prevented. It is also possible to stop answering an acknowledgment or request a retransmission in a preferred manner.

According to a further embodiment d), the communication according to the second and third relay stations HS2, HS3 can be carried out, wherein at least one of the second relay stations HS2 has access to the information of at least one other third relay station HS3 in order to relay the information according to it The situation is judged on the basis that the data D cannot be received optimally in a possible manner.

Surprisingly, it is even preferable to unconditionally switch a) the data D already irrelevant for the evaluation and thus irrespective of the satisfactory or non-compliant reception quality in the relay station HS. If it is assumed that all data paths SS-HS1-RS; SS-HS2-RS; SS-HS3-RS have approximately the same average packet error rate PER ₀ , then a total of K relay stations arranged parallel to each other exactly The probability that n relay stations can correctly receive a transmitted data packet can be formulated as follows:

$\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; K</span>}\\ \mathrm{<span\; class="notranslate">\; no</span>}\end{array}\right)<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; PER</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{{\mathrm{<span\; class="notranslate">\; PER</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; .</span>$

The average number of relay stations that correctly receive and forward packets or data accordingly is calculated as follows;

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&ap;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; PER</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; .</span>$

During the common transmission in the SFN communication system when all K intermediate stations switch unconditionally, in the case of condition-dependent switching, that is, according to the preferred embodiment, the received data D is evaluated in the relay stations HS1-HS3. In the case of reception quality, only data D reaches the receiving station via a smaller number of data paths SS-HS1-RS; SS-HS3-RS. As a result, in the case of a condition-dependent handover, the reception power of the receiving station RS may be comparatively lower than in the case of an unconditional handover of the data D via all relay stations. However, in the case of a partial blocking of the transfer, the data D received by the receiving station RS has a higher data quality or a lower signal-to-noise ratio, so that an improvement in the data quality may be registered entirely.

Claims (9)

1. Method for transmitting data (D) in a communication system (MHSFN), wherein - the data (D) is transmitted from the transmitting station (SS) to the receiving station (RS) receiving the data (D) via at least 2 relay stations (HS1, HS2, HS) which respectively receive the data and relay the data, and - the data (D) may be retransmitted if it is insufficient for transmission at the request of the receiver and/or in the absence of an acknowledgment (ACK) from the receiver, It is characterized in that, A request or acknowledgment (ACK) is only generated by the receiving station (RS) and transmitted back to the transmitting station (SS). 2. The method of claim 1, wherein At least one of the relay stations (HS2) can check the received data (D) which is not sufficient for reception, and the data (D) is either not forwarded or forwarded depending on the check result, and/or if related to the check result In relevant cases, the data communication connection (V22) via the relay station (HS2) can be interrupted in the transmitting station (SS) without a new request. 3. A method according to claim 1 or 2, wherein The data (D) is only transmitted via one of the relay stations (HS1, HS3) that receives the data (D) well enough. 4. A method according to claim 2 or 3, wherein In at least one of the relay stations (HS2, HS3) prior to forwarding the received data (D) received, in at least one of the relay stations (HS2, HS3), to identify whether the received data conform to the requirements or not, error correction methods (ARQ, CRC) or error detection methods can be used . 5. Method according to any one of the preceding claims, wherein In at least one relay station (HS2), the forwarding of the received data (D) to at least one parallel relay station (HS3) is carried out or not, depending on its own reception quality and on reception quality information. 6. Method according to any one of the preceding claims, wherein The transmitting station (SS), the receiving station (RS) and at least a part of the relay stations (HS1-HS3) all belong to a communication system (MHSFN) which communicates on a single frequency. 7. Method according to any one of the preceding claims, wherein The data (D) is forwarded via different parallel paths formed by different relay stations (HS1; HS2; HS3), wherein the data (D) is processed, in particular distorted and/or corrected, decoded and/or encoded in the relay station. 8. Method according to any one of the preceding claims, wherein The data (D) transmitted in parallel via different paths are received superimposedly at the receiving end and processed together. 9. A communication station (RS, SS, HS1, HS2, HS3) implementing the method according to claim 1, wherein A communication station constituted as a relay station (HS1-HS3) has - a receiving device (R) to receive the data to be forwarded (D), - an analyzing device (A) to analyze this data (D) according to its reception quality, and - A transmitting device (S) to relay the data (D) in relation to the results in the analysis device.